Direct chemical in-depth profile analysis and thickness quantification of nanometer multilayers using pulsed-rf-GD-TOFMS

• Published in: Analytical and bioanalytical chemistry Vol. 396; no. 8; pp. 2881 - 2887
• Main Authors: Valledor, R, Pisonero, J, Bordel, N, Martín, J. I, Quirós, C, Tempez, A, Sanz-Medel, A
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.04.2010; Springer-Verlag; Springer
• Subjects: Analysis; Analytical Chemistry; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Exact sciences and technology; Food Science; Laboratory Medicine; Mass spectrometry; Mathematical analysis; Monitoring/Environmental Analysis; Multilayers; Original Paper; Spectrometric and optical methods; Nanometer layers; Depth profile analysis; Useful yield; Mass spectrometry; Glow discharge; High resolution; Chemical analysis; Magnetron; Sputtering; Pulsed discharge; Depth resolution; Depth profile; Standard curve; Quantitative analysis; Multilayer; Sample; Estimation; Use; Radiofrequency; Bilayer; Layer thickness; Operating conditions; Substrate; Time of flight method; Yield
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-009-3382-8

Nanometer depth resolution is investigated using an innovative pulsed-radiofrequency glow discharge time-of-flight mass spectrometer (pulsed-rf-GD-TOFMS). A series of ultra-thin (in nanometers approximately) Al/Nb bilayers, deposited on Si wafers by dc-magnetron sputtering, is analyzed. An Al layer is first deposited on the Si substrate with controlled and different values of the layer thickness, t Al. Samples with t Al = 50, 20, 5, 2, and 1 nm have been prepared. Then, a Nb layer is deposited on top of the Al one, with a thickness t Nb = 50 nm that is kept constant along the whole series. Qualitative depth profiles of those layered sandwich-type samples are determined using our pulsed-rf-GD-TOFMS set-up, which demonstrated to be able to detect and measure ultra-thin layers (even of 1 nm). Moreover, Gaussian fitting of the internal Al layer depth profile is used here to obtain a calibration curve, allowing thickness estimation of such nanometer layers. In addition, the useful yield (estimation of the number of detected ions per sputtered atom) of the employed pulsed-rf-GD-TOFMS system is evaluated for Al at the selected operating conditions, which are optimized for the in-depth profile analysis with high depth resolution.